Showing papers on "Precipitated silica published in 2019"

Surface-Induced Silica Scaling during Brackish Water Desalination: The Role of Surface Charge and Specific Chemical Groups

Abstract: Silica scaling of membranes used in reverse osmosis desalination processes is a severe problem, especially during the desalination of brackish groundwater due to high silica concentrations. This problem limits the water supply in inland arid and semiarid regions. Here, we investigated the influence of surface-exposed organic functional groups on silica precipitation and scaling. A test solution simulating the mineral content of brackish groundwater desalination brine at 75% recovery was used. The mass and chemical composition of the precipitated silica was monitored using a quartz crystal microbalance, X-ray photoelectron spectroscopy, and infrared spectroscopy, showing that surfaces with positively charged groups induced rapid silica precipitation, and the rate of silica precipitation followed the order -NH2 ∼ -N+(CH3)3 > -NH2/-COOH > -H2PO3 ∼ -OH > -COOH > -CH3. Force vs distance AFM measurements showed that the adhesion energy between a silica colloid glued to AFM cantilever and the studied surfaces increased as the surface charge changed from negative to positive. Thus, for the first time direct measurements of molecular forces and specific chemical groups that govern silica scaling during brackish water desalination is reported here. The influence of the different functional groups and the effect of the surface charge on silica precipitation that were found here can be used to design membranes that resist silica scaling in membrane-based desalination processes.

Production and characterization of precipitated silica from palm oil mill fly ash using co2 impregnation and mechanical fragmentation

Abstract: In this research, sol-gel precipitation using CO2 impregnation and mechanical fragmentation method was applied to produce precipitated silica from Palm Oil Mill Fly Ash (POMFA). Carbon dioxide (CO2) was used in order to reduce the cost of the process and to enable sodium hydroxide recovery. The precipitation process was done in a stirred temperature-controlled baffled glass precipitator. The response surface method with the central composite design was applied to optimize the stirring speed and the CO2 flow rate. The pH and the temperature of the precipitation process were varied for tailoring the specific surface area of the precipitated silica. The mechanical fragmentation and wet crushing process were applied to control the agglomerate particle size of the precipitated silica obtained. The results show that precipitated silica with a specific surface area in the range of 50 - 140 m2/g can be obtained.

Interfacial phenomena at a surface of individual and complex fumed nanooxides

Abstract: The aim of this review paper was to analyze investigation results on interfacial and temperature behaviors of nonpolar and polar adsorbates interacting with individual and complex fumed metal or metalloid oxides (FMO), initial and subjected to various treatments or chemical functionalization and compared to such porous adsorbents as silica gels, precipitated silica, mesoporous ordered silicas, and polymeric composites. Note that the particulate morphology of FMO depends strongly not only the flame reaction conditions but also on the types and amounts of reagents, as well their distribution in the flame. Therefore, complex nanooxides can include core-shell nanoparticles, (CSNP) of 50-200 nm in size with titania or alumina cores and silica or alumina shells in contrast to simple and smaller nanoparticles of individual FMO. CSNP could be destroyed under high-pressure cryogelation (HPCG) or mechanochemical activation (MCA). These treatments as well simple hydrocompaction (controlled wetting-drying) affect the structure of aggregates of nanoparticles and agglomerates of aggregates, resulting in their becoming more compacted. The analysis shows that complex FMO could be more sensitive to external actions than simple nanooxides such as fumed silica. Any treatment of ‘soft’ FMO affects the interfacial and temperature behaviors of polar and nonpolar adsorbates. Rearrangement of secondary particles and surface functionalization affect the freezing-melting point depression of adsorbates. For some adsorbates, open hysteresis loops became readily apparent in adsorption-desorption isotherms. Clustering of adsorbates bound in pores causes reduced changes in enthalpy during phase transitions (freezing, fusion). Freezing point depression and melting point elevation cause significant hysteresis freezing-melting effects for adsorbates bound to initial and treated FMO in textural pores (voids between nanoparticles in secondary structures). Relaxation phenomena for both low- and high-molecular weight adsorbates or of filled polymeric composites are affected by the morphology of primary particles, structural organization of secondary particles of differently treated or functionalized FMO, content of adsorbates, co-adsorption order, and temperature.

Siliplant1 (Slp1) protein precipitates silica in sorghum silica cells

Abstract: Summary Silicon is absorbed by plant roots as silicic acid. The acid moves with the transpiration stream to the shoot, and mineralizes as silica. In grasses, leaf epidermal cells called silica cells deposit silica in most of their volume by unknown mechanism. Using bioinformatics tools, we identified a previously uncharacterized protein in sorghum (Sorghum bicolor), which we named Siliplant1 (Slp1). Silica precipitation activity in vitro, expression profile, and activity in precipitating biosilica in vivo were characterized. Slp1 is a basic protein with seven repeat units rich in proline, lysine, and glutamic acid. A short peptide, repeating five times in the protein precipitated silica in vitro at a biologically relevant silicic acid concentration. Raman and NMR spectroscopies showed that the peptide attached the silica through lysine amine groups, forming a mineral-peptide open structure. We found Slp1 expression in immature leaf and inflorescence tissues. In the immature leaf active silicification zone, Slp1 was localized to the cytoplasm or near cell boundaries of silica cells. It was packed in vesicles and secreted to the paramural space. Transient overexpression of Slp1 in sorghum resulted in ectopic silica deposition in all leaf epidermal cell types. Our results show that Slp1 precipitates silica in sorghum silica cells.

Synthesis and formation mechanism of porous silicon carbide stacked by nanoparticles from precipitated silica/glucose composites

Abstract: Porous silicon carbide (SiC) with a Brunauer–Emmett–Teller specific surface area of 75 m2 g−1 and a pore volume of 0.37 cm3 g−1 was synthesized through a facile process using industrial precipitated silica and glucose. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy analyses indicated that the SiC was stacked by β-SiC nanoparticles with size ranging from 60 to 150 nm, and its morphology was similar to that of precipitated silica. Further analysis showed that the formation mechanism of porous SiC was different from the general carbothermal reduction method. The proposed mechanism indicated that precipitated silica is a porous particle stacked by amorphous primary silica nanoparticles. When the temperature was higher than its softening point during the carbothermal reduction reaction, the silica nanoparticles softened and began to change from solid phase to liquid phase with a certain viscosity. Then, the pyrolytic carbon of glucose in contact with silica nanoparticles was diffused into the liquid phase and reacted in situ to form SiC. Precipitated silica served as a template, and SiC inherited its morphology and structure.

Why fumed and precipitated silica have different mechanical behavior: Contribution of discrete element simulations

Abstract: Precipitated silica (PS) could be an interesting alternative to fumed silica (FS) for the core of Vacuum Insulation Panels (VIP), in particular to reduce their cost and widen their use. However, compacted PS exhibits, for the same density, lower mechanical properties than FS. A better understanding of the mechanical behavior of these materials would help to design PS with optimized mechanical properties for VIP. In this work, complemented with experimental characterization, Discrete Element Method (DEM) simulations are used to investigate the compaction behavior and post-compaction tensile behavior of a set of numerically generated silica aggregates with varying neck size, surface energy and morphology (primary particle size, fractal dimension and gyration radius). During the compaction stage, neck size has the largest influence on the mechanical behavior, whereas during the tensile stage the influence of surface energy predominates. These results should be taken with caution as the task of modeling such a complex system necessarily involves bias due to simplifying assumptions. However, it is believed that the experimentally observed differences between PS and FS in compaction behavior and strength may lie not only in aggregates morphological differences, but also in different surface energies and neck sizes.

The effect of photoactivated transformations of Ag + and Ag 0 in silica fillers on their biocidal activity

Abstract: Ag and AgCu containing powdered silica fillers of polymers for medical applications have been synthesized using mechanochemical activation with a low content of solvent or dry powdered materials. The samples in the form of filled polymer films were obtained using polyurethane-urea and silica nanocomposites. The composites have been investigated by TEM, UV/Vis spectroscopy, XRD and microbiological analysis. It has been found that amorphous and nanosized structures of silver oxides and metallic Ag nanocrystallites are formed during thermal destruction of silver nitrate or ammonium complexes in silica matrix (fumed or precipitated silica). Sunlight exposure of nanocomposites contained Ag+ ions leads to the formation of Ag0 nanocrystallites. After UV irradiation, the decrease in surface plasmon resonance band intensity can be caused by the oxidation of Ag0. It is found that silica nanocomposites with the low Ag content (0.2 mmol g−1 SiO2) exhibited the highest antimicrobial activity, whereas the polymeric film with a filler content of 1 wt% exhibited the most efficient antimicrobial properties among tested polymeric composites. The observed transformations (Ag+ ↔ Ag0) of silver compounds do not suppress the biocidal activity of nanocomposites.

Nanostructured Amorphous Silicas Hydrophobized byVarious Pathways

Abstract: Various nanostructured amorphous silicas [fumed silicas such as crude (A-300), hydro-compacted (cA-300, TS 100), and precipitated silica Syloid 244] were modified by different polydimethylsiloxanes such as PDMS5, PDMS100, PDMS200, PDMS1000, and PDMS12500 (the label numbers show the viscosity (η) values) using dimethyl carbonate (DMC) as a siloxane-bond-breaking reagent. In addition, hexamethyldisilazane was used to modify fumed silica cA-300. The nanocomposites were characterized using microscopy, infrared spectroscopy, thermodesorption, nitrogen adsorption-desorption, solid-state NMR spectroscopy, small-angle X-ray scattering, and zeta-potential methods. It was found that the morphological, textural, and structural characteristics of silicas grafted with PDMS depend strongly not only on the type and content of the polymers used but also on the organization of nonporous nanoparticles (NPNP) in secondary structures (aggregates of NPNP and agglomerated aggregates, ANPNP), as well on the reaction temperature (Tr). Specifically, we determined that ANPNP with a macro/mesoporous character are favorable for the effective modification of the silicas studied with short polymers and no DMC addition but at higher temperatures or for a longer silicone polymer with the presence of DMC and at lower temperatures. In particular, the PDMS/DMC-modified silicas are of great interest from a practical point of view because they remain in a dispersed state with no strong compaction of the secondary structures after modification, and this corresponds to a better distribution of the modified nanoparticles in polymeric or other matrices.

Grass silica mineralizer (GSM1) protein precipitates silica in sorghum silica cells

Abstract: Summary Silicon is absorbed by plant roots as silicic acid. In shoot tissues, silicic acid mineralizes as silica by completely unknown mechanisms. Most prominently, leaf epidermal cells called silica cells deposit silica in most of their volume. Using bioinformatics tools, we identified a previously uncharacterized protein in sorghum (Sorghum bicolor), which we named as Grass Silica Mineralizer (GSM1). We characterized the expression profile and demonstrated its activity in vitro and in vivo. GSM1 is a basic protein with seven repeat units rich in proline, lysine and glutamic acid. We found GSM1 expression in immature leaf and inflorescence tissues. In the active silicification zone of sorghum leaf, GSM1 was localized to the cytoplasm or near cell boundaries of silica cells. GSM1 was packed in vesicles and secreted to the paramural space. A short peptide, repeating five times in the protein precipitated silica in vitro at a biologically relevant silicic acid concentration. Raman and NMR spectroscopies showed that the peptide attached the silica through lysine amine groups, forming a mineral-peptide open structure. Transient overexpression of GSM1 in sorghum resulted in ectopic silica deposition in all leaf epidermal cell types. Our results show that GSM1 precipitates silica in sorghum silica cells.

Instrumented Indentation of Super-Insulating Silica Compacts

Abstract: Highly porous silica compacts for superinsulation were characterized by instrumented indentation. Samples showed a multi-scale stacking of silica particles with a total porous fraction of 90 vol %. The two main sources of silica available for the superinsulation market were considered: fumed silica and precipitated silica. The compacts processed with these two silica displayed different mechanical properties at a similar porosity fraction, thus leading to different usage properties, as the superinsulation market requires sufficient mechanical properties at the lowest density. The measurement of Young's modulus and hardness was possible with spherical indentation, which is an efficient method for characterizing highly porous structures. Comparison of the mechanical parameters measured on silica compacts and silica aerogels available from the literature was made. Differences in mechanical properties between fumed and precipitated compacts were explained by structural organization.

Synthesis of silica from rice husk using acid pretreatment and its characterization

Abstract: The research describes the extraction of silica from rice husk by acid alkaline precipitation method with different temperatures. The used of different temperature influenced the morphology of the silica. Rice husk known as local agriculture waste and the technology has been evaluate to less the production of agriculture waste. In this research, precipitation process has been chosen as it low cost, low toxic and less the energy process compared to the other process. According to the Fourier Transform Infrared (FTIR) results, the peaks of Si-O-Si were found when the samples were sintered from 600 °C to 1200 °C. X-Ray Diffraction (XRD) patterns showed the crystallization of amorphous silica became dominant when the temperature is increased. Morphology of silica nanoparticles has been observed under Field Emission Scanning Electron Microscope (FE-SEM) analysis. In this study, precipitated silica can be successfully synthesized using acid alkaline precipitation method.

Silica grafted with epoxidized liquid polybutadienes: evidence for the mechanism of reinforcement

Abstract: Precipitated silica with backbone epoxidized liquid polybutadiene grafted onto its surface has recently been presented as a new reinforcement material that requires significantly less ener...

Engineering Behavior of Dredged Soil with Precipitated Silica

Abstract: In this study, it is proposed to improve the dredged soil extracted from Narayanapuram Lake of Chennai using precipitated silica. Dredged soil is a universally known soil waste produced while dredging of lakes, seas, rivers and dams. The dredged soils when accumulated in large quantities pose a serious threat for disposal and environment all around the world. Though in abundant, the strength parameter of dredged soil won’t agree with the foundation requirements. So there is a huge need for improving such soils. One of the commonly used high performances thickening agent in chemical industries is precipitated silica. It is formed by the reaction of an alkaline silicate solution with mineral acid. Dredged soil was collected, dried, pulverized and the basic index and engineering properties tests were carried out by varying the percentage of precipitated silica with respect to the weight of the dredged soil. Desirable results were obtained and the optimum percentage of precipitated silica was derived using the experimental investigations conducted in the laboratory. Detailed investigation of dredged soil carried out in the laboratory revealed that the addition of 4% of precipitated silica with loose dredged soil improved its shear strength by 42.85% and makes it dense.

Preparation method of precipitated silica abrasive for toothpaste

Abstract: The invention relates to a preparation method of a precipitated silica abrasive for toothpaste. The raw materials for the precipitated silica abrasive include sodium silicate, sulfuric acid, sodium sulfate and tap water. The sodium sulphate is sodium sulphate recovered from a mother solution in a reaction kettle, the production cost is reduced by adopting direct steam heating, three-stage sulfuricacid adding reaction is adopted in the synthesis process, and the uniformity and dispersibility of particles are ensured. The method is simple and easy to operate, and the product quality stability can be ensured. The precipitated silica obtained by using the method has the characteristics of small specific surface area and excellent friction effect and is suitable for use as the precipitated silica abrasive. The precipitated silica abrasive is characterized in that pH is 6.5-8.5; a DBP oil absorption value is 80-100 ml/100 g, the water absorption amount is 15-18 ml/20 g, the BET specific surface area is 40-60 m /g, and the average particle size is 10-13 microns.

Experimental Studies on Different Proportions of CB-Filled Natural Rubber Composites with Precipitated Silica and Silica Gel

Abstract: Effect of silica and silica gel with natural rubber composites was studied through mechanical properties and morphological studies. In this work, natural rubber blends with carbon black (CB) and silica as composite material-1 and natural rubber blends with CB and silica gel as composite material-2 were synthesized by two-roll-mill process followed with hydraulic press at specified operating conditions. These composite materials were investigated with each other in different proportions of sample with regard to the tensile strength, tensile modulus, and elongation at break, tear strength and hardness. The composite material-1 found to be a greater improvement in the physical properties in comparison with the composite material-2 in all same proportions. Morphology results revealed that silica adding up composites had strong interfacial adhesion and uniform dispersion into the rubber matrix, whereas silica gel had weak adhesion and improper dispersion. Comparison study also carried out with virgin natural rubber vulcanizates. Based on results, silica could be a suitable filler material than the silica gel for improving natural rubber composites performance in the basis of reliability and durability.

Precipitated silica for low-viscosity toothpaste and preparation method of precipitated silica

Abstract: The invention belongs to the technical field of silica preparation, and particularly relates to precipitated silica for low-viscosity toothpaste and a preparation method of the precipitated silica. The preparation method comprises the following steps: S1, adding a sodium sulfate solution to a reaction kettle, conducting stirring and heating, and then adding a sodium silicate solution to adjust thepH value; S2, simultaneously adding a sodium silicate solution and a sulfuric acid solution for reaction, and controlling the pH value of the reaction process to be 9-10, and after the sodium silicate solution is completely added, continuing adding the sulfuric acid solution until an end point pH value, and conducting stirring to obtain a preliminary product of silica; and S3, subjecting the preliminary product of silica to pressure filtration and washing by dilute sulfuric acid, and then conducting drying, and finally conducting crushing, so as to prepare the silica. The silica of the present invention can reduce the initial viscosity of the toothpaste and inhibit the viscosity of the toothpaste from growing, enables the toothpaste to maintain a proper viscosity, a good pseudoplasticityand thixotropy, and has a good application effect.

Precipitated Silica from Sodium Silicate by CO2 on Fixed Bed Column

Abstract: The precipitated silica prepared by reaction of sodium silicate and gas CO2 on fixed bed column have been production successfully. In this study, silica from bagasse was extraction by sodium hydroxide 2N solution to produce sodium silicate solution. The sodium silicate solution was dilute by demineralize water to produce some concentration in the range of 0.33-0.98 %SiO2. Fixed bed column has a diameter of 7.5 cm with a height of 50 cm and a pH control apparatus. CO2 gas and sodium silicate liquid are both flowed from under of the column with a specified flow rate. The precipitate process was carried out on a fixed bed column with high of bed in the range of 10-30 cm. The effect of silica concentration and the high of the bed on the characterize of the precipitated silica product have been studied. The precipitated silica product characterized by XRF, XRD, SEM-EDX and BET. The quality of precipitated silica produced in the range concentration of 95-98 w% SiO2, surface area (BET) in the range of 46.1 – 58.8 m2/g.

Low-density colored silica particle with porous structure and preparation method of low-density colored silica particle

Abstract: The invention belongs to the technical field of precipitated silica and specifically relates to a low-density colored silica particle with a porous structure and a preparation method of the low-density colored silica particle. The preparation method comprises the steps: S1, dropwise adding a water glass solution into a sulfuric acid solution to prepare an acidic silica sol solution; S2, filling areaction tank with the sulfuric acid solution and hydroxyethyl cellulose, then, simultaneously and dropwise adding the acidic silica sol solution and the water glass solution, ending the operation ofdropwise adding the acidic silica sol solution, then, further and dropwise adding the water glass solution until the pH value reaches 3-4, adding a pigment, then, dropwise adding the water glass solution to reach an end-point pH value, and carrying out stirring until a gel is separated from a system; S3, adding ethanol and glycerol into the gel, and carrying out stirring; and S4, carrying out pressure filtering, drying, smashing, washing and drying on the gel to prepare the colored silica particle. The silica particle is good in suspension property, adsorption property and mild grinding property, suitable for application to household chemicals such as body wash, cleaning milk and toothpaste and good in application prospect.

Charakterizace modifikovaných částic siliky pomocí maloúhlového rozptylu rentgenových paprsků

Abstract: Bachelor thesis deals with modification of precipitated silica by various organosilanes and their characterization by small-angle X-ray scattering. Theoretical part summarizes the information about silica, which is important filler used in the rubber industry, about organosilanes, materials improving the adhesion of silica with rubber matrix, and principle of silanization. The last chapter of the theoretical part includes the description of X-ray radiation and the small-angle X-ray scattering. Experimental part deals with the modification of precipitated silica particles by four different types of organosilanes, their characterization by thermogravimetry and small-angle X-ray scattering and subsequent analysis of aggregate size changes caused by modification. Experiments have shown that silanization incerases the size of aggregates.

OTR OTR tire tread rubber compound having low heat

Abstract: The present invention relates to an OTR tire tread rubber composition for high load having low heating performance and a tire manufactured by using the same, and more particularly, to an OTR tire tread rubber composition for high load, which improves low heating characteristics by including at least two kinds of carbon blacks, precipitated silica, and a silica dispersant. According to the present invention, the OTR tire tread rubber composition comprises: with respect to 100 parts by weight of a raw rubber, 45 to 60 parts by weight of a mixed carbon prepared by mixing at least two kinds of carbon blacks, having an iodine adsorption value of 135 to 155 g/kg and a DBP adsorption amount of 105 to 115 ml/100 g; 1 to 15 parts by weight of precipitated silica having a BET adsorption value of 150 to 170 m^2/g and a DBP adsorption amount of 180 to 200 ml/100 g; and 1 to 5 parts by weight of a silica dispersant.

Comparison and Evaluation of Different Analytical Methods to Predict the In-Rubber Dispersibility of Silica

Abstract: The aim of the present investigation was to find a correlation between one single analytical parameter of precipitated silica and its in-rubber dispersibility. Therefore, 25 different types of silica with a variety of analytical parameters and dosage forms were investigated by means of standard analytical methods (CTAB, BET, DOA, pH and moisture content) as well as t*wo new methods, the sedimentation test and the in-situ cluster fragmentation. Moreover, all types of silica *were mixed inside a typical Green Tire formulation filled with 80 phr of silica. The macro-dispersion quality was evaluated by means of two dispersion measurement systems, the Topography where the surface roughness of a rubber sample is scanned mechanically by a probe and the Dispertester where the sample is investigated by an optical light microscope. No significant linear correlation between the standard analytical parameter and the macro-dispersion quality could be found whereas the sedimentation method and in-situ cluster fragmentation provides promising approaches. However, it was not possible to directly predict the in-rubber dispersibility of silica by means of one single analytical parameter with a very high correlation coefficient. Finally, different aspects which limit the general approach were discussed. Taking all these facts into account it becomes obvious that a linear correlation of one single analytical parameter with the dispersion quality cannot be found.

Methods and compositions for the surface treatment of substrates and articles obtained therewith

Abstract: The invention relates to an article with enhanced hydrophobic and/or icephobic surface properties comprising a substrate and a coating composition deposited onto the surface of said substrate, said coating composition comprising (i) one or more crosslinked polyurethane polymers and (ii) particulates of precipitated silica functionalized with a linear polyfluorinated compound presenting at least one α,ω alcoxysilane end group, said functionalized silica particulates being either embedded inside the crosslinked polyurethane polymers or deposited onto the outside surface of a separate layer of said crosslinked polyurethane polymers. The invention also relates to a method to prepare such article, and to the functionalized precipitated silica particulates used therein.

Medical filler composition

Abstract: Disclosed is a medical filler composition, which is loaded in a space which is empty due to the removal of nerves, blood vessels, cell tissues and hard tissues therefrom and which is also biocompatible, highly bioactive and biochemically stable and has high workability and sealing ability, including a calcium supply source including at least one selected from among calcium hydroxide and calcium oxide, a silicon supply source including at least one selected from fumed silica, precipitated silica, colloidal silica and clay mineral, and 20 to 70 parts by weight of a liquid material for pasting, based on 100 parts by weight of a mixture of the calcium supply source and the silicon supply source, wherein the calcium/silicon molar ratio of calcium silicate hydrate produced by a pozzolanic reaction between the calcium supply source and the silicon supply source is 025 to 15